Prevention of foaming in steam generation



Patented Mar. 11, 1952 PREVENTION OF FOAMIN G IN STEAM GENERATION Paul G. Bird and Arthur L. Jacoby, Western Springs, 111., assignors to National Aluminate Corporation, Chicago, 111., a corporation of Delaware No Drawing. Application December 23, 1946, Serial No. 718,120

6 Claims.

The present invention relates to antifoaming compositions which are used in steam boilers and similar steam generators, evaporators, etc., to overcome the tendency of the water therein to foam and hence to bring about the priming of the steam generator or the like.

This application is a continuation-in-part of our co-pending application Serial No. @6589, filed March 27, 1942, now abandoned.

It is well known in the operation of steam boilers, such as in electric power plants, railroad locomotives and the like, or in evaporators, that the water therein, even though initially it shows very little tendency to foam, will, when the amount of total solids therein approaches a relatively high concentration, develop a very decided tendency to foam. When this occurs, considerable quantities of water are physically carried out of the boilers or evaporators with the steam, thus appearing in the steam lines and in the eventual condensate. Such priming has many disadvantages because it tends to contaminate the steam lines, to plug or corrode the valves, and under serious conditions may even impair the cylinders and piston rods of the steam engines, or the impeller blades of turbines in which the steam is used for the generation of power.

Attempts have been made in the past to control this foaming, by excessive blowdown of the boilers or by the injection thereinto of such materials as castor oil, tallow, and the like. While these fatty materials have some small degree of efiiciency, they are, on the other hand, quite deficient in that they introduce new dimculties which, in some instances, are worse than the conditions they are intended to cure. In the first place, these fatty acids or glycerides are unstable under the conditions existing in the boilers, particularly as the pressure and temperature increase, the high temperatures leading to rapid decomposition of the glycerides, which, if anything, will tend to increase the foaming and priming difiiculties. Furthermore, in many instances certain of the decomposition products thus produced, or sometimes even the materials themselves, have a definite volatility with steam and will, therefore, steam-distil out of the boilers, thus appearing in the steam and in the condensate. This, of course, is also very undesirable. Furthermore, such types of antifoaming agents usually have to be employed in relatively large quantities, adding not only to the expense but also to the inconvenience of operating the steam generators; and those which have a tendency to decompose do so quite rapidly, and hence their effectiveness is of short duration, which therefore necessitates the continual charging into the boilers or other steam generators of relatively large amounts of these older antifoaming agents. Moreover, such antifoaming agents are diflicult to use because the amounts in which they are efiicacious are very critical, and any overdosage usually aggravates the difliculty instead of curing it.

One of the objects of the present invention is the preparation of a liquid suitable for the generation of steam in steam generators and comprising water containing dispersed therein a very small amount of a-specific type of compound whereby, when suchwater. is heated to the boiling point in a team boiler or other generator, being thereby evaporated, the concentration of solids therein will not bring about excessive foaming and the resulting priming, the added compound being substantially non-volatile with the steam and stable, so that it'will be retained by the water and neither it nor its decomposition products will appear in the steam and the resulting condensation thereof. Other objects will appear hereinafter.

In accordance with this invention, it has been discovered that there is a series of compounds which may be broadlydesignated as diacylated hydrazines where at least one acyl group contains at least 16 carbon atoms, which are useful as antifoaming and antipriming agents in steam generators operated under superatmospheric pressure conditions.

The compounds involved in the practice of the present invention can be illustrated by the structural formula:

in which X is an aliphatic radical containing a carbon chain of at least 15 carbon atoms and Z is the acyl radical of an acid from the group consisting of aliphatic carboxylic acids, aromatic carboxylic acids, aromatic-aliphatic carboxylic acids and aryl sulfonic acids.

Certain limitations as to the molecular size of the materials are known to exist, and for the sake of convenience these will be discussed by reference to three classifications into which the materials of the invention may be grouped.

The total molecular weight of the condensation products, as well as the spatial configuration, apparently has a marked effect on their efficacy as .antifoaming and antipriming agents. For the sake of convenience, the limitations ;as to the molecular size of the materials will be discussed by reference to three classifications intowhich the materials of the invention may be grouped.

3 First, we may recognize the group consisting of diacyl derivatives of hydrazines in which both acyl groups are derived from fatty acids and in which the two acylgroups are substantially equal as regards the numberiof carbon atoms in each. These derivatives we have chosen to refer to as symmetrical. In this group the total number of carbon atoms in the derivative must be 32 and is preferably within the range of 32 to 48. Examples of hydrazine derivatives of this group include distearylhydrazine, palmitylstearylhydrazine, and oleylstearylhydra zirf e. h V

Second, there is a group consisting of diacyl derivatives of hydrazines, in which both acyl groups are derived from fatty acids, but where the two groups differ widely from each other in the number of carbon atoms in each. This group we refer to as unsymmetrical, and here the total number of carbon atoms in the derivative must be at l t ab ut 8..;9. the. lemat s s hydrazine- In.c se fhydraz uatn qllauin arec ds as u sxmmetfica-Lnamelsi. .a y zi e and. butrr ru l draz nfi- Thir cl, there isthe-group consisting of diacyl vderivatives of hydrazines in which one acyl radical is derived from, afatty acid and the other acyl radical ,isthat of anaromaticcarboxylic or an arylsulfonic acid. These we refer to as mixed, and in this :group the, fatty acid radicalshould containat least about;16 carbon atoms regardless of. the size of the, other acyl radical.

We shall describe "hereinbelow the preparation of several of the materials, and while the examples disclose a few of many satisfactory preparative procedures, in most cases the same product may be obtainedby more than one route.

The'most usedmethod of preparation involved the use of the acid. and theamine, in nearly theoretical amounts for the product desired, and consisted essentially in the initial formation of the amine' salt of the acid, followed by dehydration to the amine by heating. In certain cases,

the use of the 'a'cid halide was resorted to in order 'tointrociuceanacm group. Instill another very useful procedure, the fatty acid ester was used instead of the acid itself. Thus, while any usual 'ester"can be "used, such as methyl, ethyl, glycol, etc, the gl-ycrides or the high molecular weight acids are oftenv'ery readilyobtainable and were the subject of much of the preparative work. By heating megiyen e and thehydrazine together in the proper proportions, the alkaline amine causes the ester to be split, liberating the fatty acid, which then reacts with the amine to give the amide. Usually, when using the triglycerides, such proportions were used that two of the three acid chains would be split off from the ester and used, and the remaining fatty acid monoglyceride remained in the product as a harmless by-product. However, excellent materials have also been formed where the proportion of triglyceride or other ester used was such that all the available acyl chains were used in forming the amide. Indeed, the reaction of theoretical'amounts of the hydrazine and a glycerol inonoester has yielded useful products. r

The number of differentcompound's which can be prepared is quite numerous, and'while we are giving a large numberof examples, we do not wish to be limited to those specifically described nor to the species claimed. These examples are as follows:

A mixture of 13.5 gra l s of commercial stearic acid (having a'ihean Iiiolecular weightof 269) and 3 grams of a 42% aqueous solution of hydrazine hydrate was heated carefully with stirring until the most of the water had been expelled and foaming had ceased. Then the mixture was stirredfor 3 hours at degrees to 166 degrees C.

hen cool, the product was a high-melting, lightcolored wax.

Example II A condensation between 25.6 grams of palmitic acid and 6 gram of 42% aqueous hydrazine hydrate solutionwas carried out as described in Example I. When cool, the product was a white wax.

Example III A condensation between 14.1 grams of oleic acid and 3 grams of 42% aqueous hydrazine hydrate solution was carried out as described in Example I. When cool, the product was a light tan Wax. a Efc'i'ni'p'l "IV A condensation between 6.7 grams of commercial stearic acid and 5grams of 42 aqueous hydrazine hydrate solution was carried out as described in Example I. Then 3.4 grams of phenylacetic acid was added thernixture stirred at 150 degrees to degrees C. for 2 hours longer. When cool, the product was a brown wax.

Example V Step I .A mixture of 13.5 grams of commercial stearic acid and 6 grams of 42% aqueous-hydrazine hydrate solution was heated carefully with stirring until the most of the water had been'expelied and foaming 'had ceased. Then the mixture was stirred at 150 degrees to 160 degreesC.

for 2 hours. I

Step II.--Then 3.5 cc. of acetyl chloride was added at 150 degrees C. andallowed to react with stirring for 15 minutes. When cool, the product was a yellow wax.

Example VI A condensation in two steps was carried out between 6.4 gram of palmitic acid, 45 grams of 42% aqueous hydrazine hydrate solution,'and 1.96 grams of acetyl chloride, as described in Example V. When cool, the product was a hard, white wax.

Example VII Example 1X A condensation in two steps was carried out between 6.7 grams of commercial stearic acid, 4.5 grams of 42% aqueous hydrazine hydrate solution, and 4.6 grams of p-nitrobenzoyl chloride, as described in Example V. When cool, the-product was a dark brown wax.

7 Example X A condensation in two steps was carried out between 6.7 grams of commercial stearic acid, 4.5 grams of 42% aqueous hydrazine hydrate solution, and 4.8 grams of p-toluene-sulfonyl chloride, as described in Example V. When cool, the prodnot was a brown wax.

The products hereinabove described, While not ordinarily considered as soluble in water to any great extent, may be suitably dispersed in water or emulsified therewith, so that effective amounts thereof may be introduced and be present in the water within the steam generator under operating conditions. The emulsifying or dispersing agent used must, however, be of a kind that does not cause foaming, either by itself or by its decomposition products. The compounds may be used conjointly with each other as Well as with other known antifoaming agents, such as, for example, castor oil.

The amounts of these high molecular weight diacyl derivatives of hydrazines which are required are extremely small, and in general one grain per gallon is ample. For many purposes, however, amounts of as little as /100 grain per gallon in the feed water will still give valuable results, and the amounts may be even further reduced. For example, /100 grain per gallon of this type of condensation product will suppress foam in a boiler for from 15 to 20 minutes. Comparing this with the efiicacy of castor oil used on the order of T 6 grain per gallon, which will suppress the foam for only about 30 seconds to one minute, it is obvious that if one were to use castor oil it would have to be continuously fed into the boiler, with the unavoidable accumulation in the boiler of a lot of soap produced by the reaction of the liberated fatty acids with the alkali present in the water, which would only aggravate the problem. The diacyl derivatives under discussion, however, are quite stable and do not yield undesirable by-products.

Depending of course, upon the degree of concentration of solids, the dosage may be varied, but one grain per pallon it about as much as would ever have to be used even under serious conditions, and for many purposes /100 grain per gallon and even less can be used. The process is particularly effective at pressures of about 2 pounds per square inch.

The introduction of the antifoaming compounds of the present invention into the boiler may be accomplished in a number of ways. Thus, the antifoaming compositions may be dispersed or physically mixed with, say, sodium carbonate or some other material used for treating the boiler water and pumped with the feed water into the boiler by means of either an injector or a feed water pump. The compounds may also be dissolved in suitable organic water-miscible solvents such as alcohols, ethers, ketones, etc., and introduced in small measured amounts into the feed water entering the boiler. Suitable mechanical measuring devices which will periodically or continuously inject the required dosage of the antifoaming compounds into the feed water may be used, so that the introduction will be more or less in proportion to the steam consumption to which the steam generator is subjected. Another manner of introducing the antifoaming compounds is to form an emulsion thereof in water and then feed said emulsion either directly into the boiler or the feed water lines leading to it.

The preferred active antifoam ingredients are oily to waxy substantially water insoluble substances characterized by stability in hot aqueous 6 alkaline liquids'such as arefused in locomotive boilers and under the conditions which arepresient in locomotive boilers. Compositions prelpared in accordance with the invention have been "demonstrated to be particularly effective in locomotive boilers under superatmospheric pressure conditions within-the range of 150 to 300 pounds per square inch and the corresponding temperature conditions. Tests have demonstrated that these compositions'are efiective even at the much higher pressure and temperature conditions in stationary boilers for power plant operations, as; for example, superatmospheric pressures up to 1000-4500 pounds per square inch.

Apart from the fact that the preferred active antifoam ingredients function under severe conditions where other so-called antifoam materials are ineffective, the reason for the functioning of these materials is not known. It has been proven in tests connected with the practice of this invention that these materials are very stable to hy' drolysis as compared with many other different types of compounds.

The amounts of an antifoam agent employed in inhibiting foam will depend upon several fac-' tors, among them the conditions under which the foam occurs, the amount of foam suppression desired, the per cent of solids in the foaming liq' uid, the alkalinity, temperature, and pressure of the foaming liquid, the type and degree of agitation, and the kind of gas present in the gas phase of the foam. It is, therefore, impossible to state any rigid rules for estimating the amount of an antifoam which needs to be used. In general, the antifoam will be added in relatively small amounts, gradually increasing in size, until the foam is controlled to the extent desired.

In the prevention of priming in a power plant or locomotive boiler operating at ordinary pressures, e. g., 250 pounds, it has been found that the effective antifoam requisite molecular size for this use, as explained above, are efiicient when they are introduced into the feed water at a concentration of the order of magnitude of 0.01 grain per gallon, based on the weight of active antifoam ingredient. Thus, a boiler operating at 10 concentrations, which is not unusual, would have 0.1 grain of active antifoam per gallon of boiler water. Some foam suppression has been obtained with only 6 parts by weight of the active ingredient per billion of water in the feed water going to a boiler. Quantities of from to 500 parts by weight of the active ingredient per billion of water are frequently sufficient merely to improve steam quality. Such proportions have allowed some users to operate with increased dissolved solids of as much as 15% over the amount permissible Without the steam conditioner. Having thus described the invention, what we claim as new and desire to secure by Letters Patent of the United States is:

1. A method of generating steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of distearyl hydrazine, said quantity being suificient to substantially inhibit said foaming and priming.

2. A method of generating steam which comprises boiling, under superatmospheric pressure conditions, water containing an amount of total dissolved solids tending to produce foaming and priming and a quantity of dioleyl hydrazine, said quantity being suflicient to substantially inhibit said foaming and priming.

3. A method of generating steam which comprises b l n und r superatmosp e i pre ure conditions, water containing an amount of total dissolved o d n in to produce foam g and prim n and a quant ty of a e l s e h drazine, said quantity being sufiicient to substan l y b t said oamin and pr min 4 The m d of generating steam o a boiler wa er havin a nd nc o foam on b ins Which comp ses d spersi int sa d Wat r a compound from the roup co sist ng of diacy hy raz n s in which both cyl up are d r v d from fatty acids, are su stantial y equal as regards the number of carbon atoms in each and the total number of carbon atoms in said hydrazine compound is at least 32, diacyl hydrazines in which one of said acyl. roups is derived from fatty acids containing 2 to 4 carbon atoms, inclusive, and the other of said acyl groups is derived from fatty acids containing at least 16 carbon atoms and the total number of carbon atoms in said hydrazine compound is at least 18, diacyl hydrazines in which one acyl radical is derived from a fatty acid containing at least 16 carbon atoms and the other acyl radical is that of an aromatic carboxylic acid, diacyl hydrazines in which one acyl radical is derived from a fatty acid containing at least 16 carbon atoms and the other acyl radical is that of an aryl sulfonic acid, and diacyl hydra-zines in which one acyl radical is derived from a fatty 8 acid containing at least 16 carbon atoms and the other acyl radical is that of an aromaticaliphatic carboxylic acid, said compound being dispersed into said water in an amount suflicient substantially to inhibit the tendency of said water to foam on boiling, and boiling said water.

5. The method of generating steam from a boiler Water having a tendency to foam on boiling which comprises dispersing into said Water stearyl phenylacetyl hydrazine in an amount sufficient substantially to inhibit the tendency of said water to foam on boiling, and boiling said water.

6. The method of generating steam from a boiler water having a tendency to foam on boiling which comprises dispersing into said water stearyl benzoyl hydrazine in an amount sufficient substantially to inhibit the tendency of said water to foam on boiling, and boiling said water.

PAUL G. BIRD. ARTHUR L. JACOBY.

REFEEEENGES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,328,551 Gunderson Sept. 7, 1943 2,442,768 Gunderson June 8, 1948 

4. THE METHOD OF GENERATING STEAM FROM A BOILER WATER HAVING A TENDENCY TO FOAM ON BOILING WHICH COMPRISES DISPERSING INTO SAID WATER A COMPOUND FROM THE GROUP CONSISTING OF DIACYL HYDRAZINES IN WHICH BOTH ACYL GROUPS ARE DERIVED FROM FATTY ACIDS, ARE SUBSTANTIALLY EQUAL AS REGARDS THE NUMBER OF CARBON ATOMS IN EACH AND THE TOTAL NUMBER OF CARBON ATOMS IN SAID HYDRAZINE COMPOUND IS AT LEAST 32, DIACYL HYDRAZINES IN WHICH ONE OF SAID ACYL GROUPS IS DERIVED FROM FATTY ACIDS CONTAINING 2 TO 4 CARBON ATOMS, INCLUSIVE, AND THE OTHER OF SAID ACYL GROUPS IS DERIVED FROM FATTY ACIDS CONTAINING AT LEAST 16 CARBON ATOMS AND THE TOTAL NUMBER OF CARBON ATOMS IN SAID HYDRAZINE COMPOUND IS AT LEAST 18, DIACYL HYDRAZINES IN WHICH ONE ACYL RADICAL IS DERIVED FROM A FATTY ACID CONTAINING AT LEAST 16 CARBON ATOMS AND THE OTHER ACYL RADICAL IS THAT OF AN AROMATIC CARBOXYLIC ACID. DIACYL HYDRAZINES IN WHICH ONE ACYL RADICAL IS DERIVED FROM A FATTY ACID CONTAINING AT LEAST 16 CARBON ATOMS AND THE OTHER ACYL RADICAL IS THAT OF AN ARYL SULFONIC ACID, AND DIACYL HYDRAZINES IN WHICH ONE ACYL RADICAL IS DERIVED FROM A FATTY ACID CONTAINING AT LEAST 16 CARBON ATOMS AND THE OTHER ACYL RADICAL IS THAT OF AN AROMATICALIPHATIC CARBOXYLIC ACID, SAID COMPOUND BEING DISPERSED INTO SAID WATER IN AN AMOUNT SUFFICIENT SUBSTANTIALLY TO INHIBIT THE TENDENCY OF SAID WATER TO FOAM ON BOILING, AND BOILING SAID WATER. 